Signaling system employing glow discharges



Patented Dec. 31, 1935 UNITED STATES PATENT OFFICE SIGNALING SYSTEMEMPLOYING GLOW DISCHARGES Leland Kasson Swart, Mountain Lakes, N. 1.,as-

signor to American Telephone and Telegraph Company, a corporation of NewYork Application March 17, 1933, Serial No. 661,413

'1 Claims. (01. 2507) This invention relates to signaling systems. Moreparticularly, this invention relates to signaling systems employinglight rays for the transmission of signals. Still more particularly,this invention relates to signaling systems employing the luminousdischarge of gas filled tubes for the transmission of signals.

It is well known that when a voltage exceeding a predetermined value isimpressed across the spaced electrodes enclosed within an envelope offor example, glass, the envelope being filled with a gaseous medium suchas neon, argon, helium, or the like, the gas within the envelope willbecome ionized and a discharge will occur. When such a discharge occurs,it will be accompanied by a luminous effect which will be quitepronounced in the space bridging the electrodes.

It is one of the objects of this invention to produce a luminousdischarge between the electrodes of a gas filled tube, radiate the raysof the luminous discharge and then convert the received rays intocurrents which will correspond to those used in producing the luminousdischarge.

This invention will be better understood from the detailed descriptionhereinafter following when read in connection with the accompanyingdrawing showing one embodiment of the invention merely for the purposeof illustration.

Referring to the drawing, the reference characters N1 and N2 representtwo gas filled tubes each having an envelope of a transparent materialsuch as glass, and each enclosing a gaseous medium which may be neon,argon or helium gas, or a combination of these gases and hydrogen ormercury vapor, or any other gas which when ionized will become luminous.These gas filled tubes N1 and N2, although they appear to be closelyspaced in the drawing, may, however, be separated by great distances.

Each of these tubes includes two or more electrodes, three electrodesbeing illustrated, however, merely by way of example. Two of theseelectrodes may be called cathodes K1 and K2. and the third electrode ananode A. The two electrodes K1 and K: may be connected to each other, asshown. The tube N1 may be considered as located at the transmittingstation or in the transmitting circuit of a signaling system, and thetube N2 may be considered as part of the receiving apparatus of thesystem which may or may not be at a distant point.

The anode A and the conductor common to the cathodes K1 and m of thetube N1 are connected to a series circuit which includes a source ofpotential designated B1 and a key designated S.

The source B1 is preferably one capable of producing a direct voltagewhich is greater than the voltage required to ionize the gas within thetube N1 and break down the gaps between either or both of the electrodesK1 and K: and the anode A.

When the key S is operated so as to close its associated contact, thesource B1 will then transmit a direct voltage of large magnitude whichwill become impressed directly between both of the electrodes K1 and K:and the anode A. In response to this impressed voltage of largemagnitude, both of the gaps between the anode A and the electrodes K1and K2 will be simultaneously broken down and both of these gaps willexhibit glow discharges which are luminous. The luminous rays mayinclude infra red rays and ultra violet rays and other rays whetherluminous or non-luminous and, of course, if the glow is of violet color,the transmitted rays will for the most part be composed of the ultraviolet portion of the spectrum.

At the receiving station it will be seen that the electrodes K1 and E ofthe tube N: are connected together and the common conductor is connectedin series with a circuit which includes the winding of a vibrating relaydesignated R1, the winding of an operating relay designated R2, 9.source of potential designated B2, and the terminal of the tube N: whichis connected to the anode A of that tube. The armature and contact ofthe vibrating relay R1 are connected in a circuit which directly shuntsthe parallel discharge gaps of the tube N2 and the series winding of thevibrating relay R1. The armature and contact of the vibrating relay arealso shunted by a condenser C of large capacity and an impedance Z ofsmall magnitude, both of which are connected in series relationship. Thearmature oi. the operating relay R: and its contact are connected to acircuit D and they control the flow of current through that circuit.

The source B: may be one of direct voltage such as may be produced by astorage battery and the voltage of this source is of itseli insufilcientto properly ionize the gas within the tube N2 so as to break down thegaps between either of the electrodes K1 and K2 and the anode A 01' thetube N2. However, when the luminous rays emanating from the electrodesand gas within the tube N1 associated with the transmitting circuit aretransmitted through the envelope of the tube N: to the electrodes K1 andm of the tube N2, the gas within the tube N2 will become instantlyionized. This will result in a reduction of I impedance between anode Aand cathodes K1 and & from a substantially infinite value to a finiteand low value. This reduction in impedance from an open circuit to aclosed circuit condition results in a current fiow from the source B2through the circuit including the winding of the operating relay R2, thewinding of the vibrating relay R1, and either or both of the electrodesK1 and K2 of the tube N2 and its anode A. The armatures of both relaysR1 and R2 will be attracted so as to close their associated contacts.Upon the closure of the contact of the relay R2, the circuit D willbecome operated.

Immediately after the armature of the vibrating relay R1 has closed itscontact, a shunt path will be established around electrodes A to K1 andK2 of tube N2 and the winding of the vibrating relay R1. The currentthen transmitted from source B2 through the winding of the relay R2 willbecome substantially increased and the increased current will retain thearmature of the relay R2 in its operated position. While the armature ofrelay R1 remains on its contact, the tube N2 will cease to glow. Thearmature of the vibrating relay R1 will release and cause the associatedcontact to become opened. Current will then fiow from the source B2through two parallel paths. One of these parallel paths will include thecondenser C and the impedance Z, causing the condenser C to becomecharged. The other path will include the anode A of the tube N2 and itstwo electrodes K1 and K2 and the winding of the vibrating relay R1. Ifno luminous light rays are transmitted from the tube N1 in thetransmitting circuit to the tube N2 in the receiving circuit, thevibrating relay will fail to return its armature to its closed positionand immediately thereafter the armature of the operating relay R2 willbecome released. If, however, rays emerging from the transmittingstation do reach the tube N2 of the receiving station, furtherionization of the gas within the tube N2 will occur and the winding ofthe vibrating relay R1 will again attract its armature and close itsassociated contact. Hence the armature of the relay R2 will remainclosed against its contact, maintaining the circuit D closed.

When the winding of the vibrating relay R1 causes the release of itsarmature, there will be produced across its contacts and hence acrossthe elements A and K1 and K2 of the tube N2 a voltage kick of largemagnitude. This kick is produced by the decay of the magnetomotive fluxin relay R2 and may of itself be sufficient, when combined with thepotential of the source 132, to ionize the gas within the tube N2,especially between electrodes A and K1 and K2 within tube N2. In orderto eliminate the possibility of this occurrence, the condenser C and theimpedance Z are interposed in the circuit, as shown, the impedance Zbeing one of comparatively small magnitude so that it may easily absorbthe voltage transmitted therethrough toward the condenser C. It will benoted that the source B2 may be one of direct current voltage and thatthe gaps within the tube N2 will become discharged only when the raysemerging from the transmitting tube N1 reach the tube N2. As long as thetube N2 receives rays of light, the relay R1 will vibrate its armatureat a high speed and the circuit D will remain closed by the armature andcontact of the relay R2. Just as soon as these emerging rays disappear,however, the gas within the tube N2 will become deionized and the circut D will be opened at the contact of the armature of the relay R2.

So it will be seen that the key S at the transmitting station or in thetransmitting circuit may be operated to create luminous discharges 5between the electrodes in the gas of the tube N1 for predeterminedintervals of time in accordance with signals. These signals will beaccompanied by the transmission of correspondingly interrupted luminousrays which will impinge upon 1 the electrodes of the tube N2 at thereceiving station. Hence the circuit of the winding of the relay R2 willbe opened and closed for moresponding intervals of time, therebycontrolling the transmission of current through the circuit D. 1

The gas filled tube N1 need not include three electrodes as shown; itmay include but two electrodes forming only one gap between which aluminous discharge will occur when the voltage across the electrodes ofthe gap exceeds a pre- 2 determined value and, in fact, it may includean external electrode (not shown). Similarly, the tube N2 may includebut two electrodes upon which the rays emerging from the transmittingstation are impinged so as to aid in thoroughly ionizing 2 the gaswithin the tube N2 and thereby reducing the impedance within the tube N2from a ve y high and practically infinite value to a very low and almostnegligible value.

The tube N1 may have the gap between its elec- 3 trodes located at ornear the foci of a parabolic reflector (not shown) which will direct thetransmission of the emerging rays accurately to the electrodes of thetube N2. Inasmuch as the parabolic reflector is not a necessary elementof 3 the system, and inasmuch as any other ray-directing device may beused instead, none has been shown in the drawing.

Neither the source B1 nor B2 need be of direct voltage. The source B2may be replaced by an 4 alternating voltage or an interrupted directvoltage. If one of the latter is employed at the source B2, it will beunnecessary to include the vibrating relay R1, the condenser C and theimpedance Z in the circuit. When the latter elements are elimi- 4 nated,the winding of the operating relay R2 will be connected in series withthe electrodes of the tube N2 and the source B2 of alternating potentialor interrupted direct potential. In the latter arrangement, the gaswithin the tube N2 5 will become deionized immediately after raysemerging from the transmitting station fail to reach the tube N2.

One of the features of this invention is the use of a gas filled tube ata transmitting station 5 which, when impressed with a sufi'iciently highvoltage, will produce a luminous glow and, when the rays of this gloware transmitted to a similar as filled tub and impressed upon theelectrodes of" thel'fia er tube with sufiicient intensity, will 6 causea prompt breakdown of the gap or gaps within the latter tube. It will beunderstood that a lens of, for example, the convex type, may beinterposed between the tubes N1 and N2 for the purpose of concentratingthe emerging light di- 65 rectly between the electrodes of the tube N2.

While other types of tubes which do not include a gaseous medium may beemployed for a light source, a gas filled tube is preferred in this in-7 vention for the reason that an illumination builds up or dies out withgreat speed. In other words, the high voltage impressed upon theelectrodes of a gas filled tube will very quickly transform the darkenedspace between the electrodes of the 7 tube into one of substantialluminosity and vice versa.

The arrangement disclosed in this application represents a substantialadvance in the art in that the operation of the relays or otherassociated electrical translating devices may be made to take placewithout the use of amplifying devices intervening betwoen the gas tubeN2 which is responsive to light and the associated electrically operatedtranslating devices. This is principally due to the current carryingcapacity of the gas filled tube which is very considerable, i. e.several amperes or more.

The operation of the gas filled tube employed in this invention differsfrom all known lightcontrolled tubes in that it employs no heatedcathode; it requires no amplifiers; it has an infinite impedance when inthe non-operating condition; it requires no resistance networks carryingcurrents at any or all times, nor does it depend upon voltage dropchanges taking place in these resistances to produce operation of theassociated electrical translating devices; nor does it depend on anelectromotive force generated by the tube itself to operate anamplifying device, for it includes no such device; and, furthermore, itdraws absolutely no current when in the non-operated condition.

The arrangement of this invention is particularly applicable for thetransmission of signals from a circuit of the type connected to tube N1,which may assume considerable potential above ground, to a circuit ofthe type connected to tube N2 which it is desired shall not assumesubstantial voltage above ground. Such a situation arises when it isproposed to transmit current from a power circuit into a telephonecircuit, or vice versa, where it becomes dificult and expensive tocouple the power line and the telephone line for the transmission ofsignals between them and avoid these large potentials in the telephoneline. This is especially true when there is a fault on the power lineand the apparatus associated with the power line may be impressed withseveral hundreds or even thousands of volts above that of the telephonecircuit. Thus the operation of the well-known protectors on thetelephone circuit will be avoided and the transmission from the powercircuit to the telephone circuit may be continued without interruptionduring these periods when, as just stated, faults exist on the powercircuit. It is obvious therefore that if the potentials applied to thetelephone circuit assumed values in excess of that required to operatethe protectors associated therewith, the circuit would be disabled at atime when it would be most needed. One of the purposes, therefore, ofthe arrangement of this invention is to enable signaling over the powerand telephone systems without danger of damage to the telephoneapparatus and without the expense of cumbersome insulating transformerswhich may, moreover, make signaling through the system with directcurrent virtually impossible.

It will be understood that a key S need not be employed at thetransmitting station or in the transmitting circuit. If the potential ofthe source B1 is applied directly between the electrodes of the tube N1,producing a continuous luminous discharge between the electrodes of thetube N1, it will then be possible to interpose between the tubes N1 andN2 any well-known form of shutter (not shown) which is eithermechanically or electrically operated. The movement of trifl the shutterwill in that case produce the interruptions in the transmitted lightwhich will correspond to the desired signals.

Inasmuch as the tubes N1 and N2 may be separated from each other byconsiderable dis- 5 tances, and inasmuch as the circuits of these tubesare separate and distinct from each other and require no physicalconnection therebetween, the glow discharge in the gas of the tube N1may be produced by lightning voltages or voltages from high voltagepower systems which may, in fact, be many thousands of volts aboveground potential. These very large voltages caused by lightning or powersurges, for example, will break down the gap or gaps of the tube N1 andlater 15 operate the relay R2 at the receiving circuit in the manneralready described hereinabove. Thus these large voltages caused bylightning, for example, may be employed to control the transmission ofextremely low voltages trans- 20 mitted through the circuits of the tubeN2, and they may similarly control small voltages or currentstransmitted through the circuit D.

It will be evident that the arrangement of this invention may be usedfor counting the 25 number of objects or devices which may pass in thepath between tubes N1 and N2. The passage of each object or device willoperate the relay R2 and close the circuit D. In such an arrangement therelay R2 may be a counting relay or, if 30 desired, the circuit D may beconnected to a counting relay or any other well-known counting devicewithout the use of amplifying devices intervening between the tuberesponsive to light and the electrically operated translating devices.

While this invention has been disclosed as embodied in certain smcificforms which may be deemed desirable, it is understood that the generalprinciples of this invention may be applied to other and widely variedorganizations without departing from the spirit of the appended claims.

What is claimed is:

1. The combination of two gas filled tubes each having two electrodes, akey, a source of poten- 4.5 tial connected in series with said key andthe two electrodes of one of said tubes, the operation of said keyapplying the potential of said source to the two electrodes of thelatter tube and producing a glow discharge therebetween, a second sourceof potential, and a relay, the winding of which is connected in serieswith said second source of potential and the two electrodes of the otherof said tubes, the luminous rays emanating from the first of said tubesbeing impressed upon the electrodes of the second of said tubes andsubstantially reducing the impedance between the electrodes of thesecond tube.

2. In a signaling system, the combination of a first gas filled tubehaving a plurality of electrodes, means for creating a luminousdischarge between the electrodes of said first tube in accordance withsignals, a second gas filled tube having a plurality of electrodes,means for impressing the rays emerging from the luminous discharge ofthe first gas filled tube upon the electrodes of the second gas filledtube and reducing the impedance between the latter electrodes from thatcorresponding to an open circuit condition to a very low impedance, anda circuit including the winding of a vibrating relay connected in serieswith the electrodes of the second gas filled tube for'periodicallyremoving all potential from the electrodes of the second tube, saidcircuit also including a current consuming 75 translating device whichis operated in accordance'with the impedance changes of the second gasfilled tube.

3. The method of signaling with apparatus including a pair of gas filledtubes each havin a pair of electrodes, which consists in intermittentlyproducing a luminous discharge between the electrodes of one of the gasfilled tubes in response to signals, transmitting the intermittentlyproduced rays of the luminous discharge to the electrodes of the othergas filled tube, reducing the impedance between the electrodes of thelatter gas filled tube from that corresponding to an open circuit valueto a very low value in response to these transmitted rays, and detectingthe signals determined by the intermittent impedance changes of thelatter tube.

4. The method of signaling by reducing the impedance between theelectrodes of a gas filled tube from that corresponding to an opencircuit condition to a very low value, which consists in transmitting tosaid electrodes and through the space between said electrodes such raysof the spectrum as are produced within the tube itself if a voltageequal to the breakdown value of the tube is impressed across itselectrodes, the transmission being interrupted in accordance withsignals, and detecting the signals determined by the intermittentchanges in impedance of the tube.

5. The combination of first and second gas filled tubes each of whichincludes two spaced electrodes, each tube having the property such thatwhen a voltage exceeding the breakdown value of the tube becomesimpressed across its electrodes a luminous discharge will occurtherebetween, means for producing in accordance with signals a luminousdischarge between the electrodes of one of the tubes, means forperiodically O u- "d supplying potential to the electrodes of the firstgas-filled tube in accordance with said signals, and means fortransmitting the rays emerging from the first gas filled tube to theelectrodes of the second gas filled tube for assisting the breakdown ofthe gap between the electrodes of the second gas filled tube.

6. The method of signaling with a pair of gas filled tubes, each havinga pair of spaced electrodes, which consists in producing a luminousdischarge between the electrodes of one of the gas filled tubes,interrupting this luminous discharge in accordance with signals,transmitting the rays of the luminous discharge and impressing said raysupon the electrodes of the other gas filled tube, reducing the impedancebetween the electrodes of the latter gas filled tube from thatcorresponding to an open circuit condition to a negligible value inresponse to the transmitted rays, and detecting the signals determinedby the alternate impedance changes within the latter gas filled tube.

"7. The combination of two similar gas filled tubes each having twoelectrodes between which a glow discharge may occur when a voltageimpressed upon said electrodes exceeds a predetermined value, said tubesbeing adjacent to each other, means for producing in accordance withsignals a glow discharge between the electrodes of one of said tubes,the emergent rays of said glow discharge being impressed upon theelectrodes of the other tube for reducing its impedance from thatcorresponding to an open circuit condition to a low value, and a currentconsuming signal detector operatlvely connected to the electrodes of thelatter tube to reproduce the signals.

LELAND K. SWART.

